A Repairman's View of Portable Minidisc Recorders

Introduction:

My remarks are mainly regarding portable recorders made by Sony, Sharp & Aiwa.
They are based on our knowledge coming from repairs we make (5 to 10 daily) on
these machines.
The first part of this paper presents typical problems with MD gear. The second part
gives a few tips about how to avoid some of those problems. The last part will try to
answer a question about the difficulty of attempting home MD repair.

A MD portable recorder is a very complicated and sophisticated machine. Let's take
for example the Sony MZ-R50, which in my opinion is the best portable recorder ever
made. The unit is built from some 600 electronic components and circa 150
mechanical parts. They all have to live peacefully inside a small box. We are talking
about 3 motors, a laser unit, disc compartment, recording head a couple of status
switches, the user interface including keyboard, LCD display, remote control & a few
sockets. In addition there is the power management including rechargeable battery,
external battery and a power supply unit (PSU). The electronic part is built around a DSP, a system
controller, RF amp, microphone pre-amp, headphone amp, A/D, D/A, memory,
motor drivers etc. In addition we can find a few flexible multi-conductors connecting
between the internal circuits and components. All the above is implemented in a
portable recorder. Some manufacturers do it better in some models and some let us
suffer. The main point to take into consideration is that the whole machine has to be
perfect in order to make it work well.

The problems:

Screws: Each MD has circa 10 screws holding the bottom cover and the upper.
The size of the screws are not the same. For instance the front screw (located near
the recording LED) on the MZ-R30/R35 is a self-taping special size. Replace it with
another type of screw and the whole mechanism will suffer. The screw holding
the arm under the cover of the MZ-R55 is a special one. Put another type and the
door will not open well. On the Sharp MD-MS7XX and Kenwood there is a screw located
near the front of the discarding lever. Replace it with a little bit longer screw and
the disc will not get out. On the back of the same machines there is a screw that,
if missing, will not let you operate the machine at all.

Recording head: Here we have a real problem. The recording head is a very
small electromagnet encapsulated in plastic and attached to a thin and flexible
piece of metal. The electric connection to the electromagnet is with a flexible thin
conductor. The connection between the electromagnet and the flexible conductor is
very sensitive and is likely to break easily. This fragile part has a relatively large
pressure on it while recording as it is forced to touch the upper surface of the
disc. Also it may break when the MD falls or if vibrated. When this part is
broken recording is impossible. Although the machine may seem to record and you
can monitor the sound while trying to record, actually it does not record. The
bad news is that this situation is very expensive to fix. As for Sony they do not
sell or replace the recording head only but the whole laser unit, which is very
expensive. This recording head problem is found largely with Sony recorders.

Power supply: In my experience this is the biggest killer of
MD's. To be more accurate, my statement is true when not using the
correct PSU. Let's say you live in Australia and buy an MZ-R55 with a
110V type PSU. You connect it to a step-down transformer as you are
doing with other 110v equipment. After a few days the machine dies
completely. If you are lucky it will live longer. The sensitivity to
PSU is mainly with new Sony models (MZR55/70/90/91) all working with
3V. The situation is better with 6V models like MZR30/35/50, and
recorders made by Sharp and Aiwa. The Sony PSU's supplied are not
regulated, they assume only small fluctuations in mains power. In
addition, the safety margin of the components meeting the PSU inside the
MD is very small.

External Jacks: Each recorder has between 3 to 5 jacks. One is
the PSU jack. Try to connect a different plug and you will probably
break the jack or the PCB or both. The white input jack on Sony and
Aiwa MD's serve as analog/optical input. The jack has in addition a
few extra functions. It is an expensive jack that we tend to break
when using cheap cables. Inside the jack there is relatively high
pressure on the plug. If the plug is a cheap or bad type you may find
that when pulling it out the tip remains inside. To extract it is
almost impossible. As for electronic problems, connecting an analog
output from a computer while it is made through the speaker output of
the sound card to the sensitive MIC input while the volume of the
computer is high can destroy the MD's mic pre-amp. Connecting the same
signal by mistake to the MD line or headphone output can damage the
line or headphone amp.

Heat and moisture: MD equipment doesn't like it. Heat can stop the machine and moisture
meeting dirt will put severe force on the mechanics.

Pressure: Sony (new models) Aiwa and Sharp have their buttons
mounted on top of the machine. Pressing too hard on the buttons in
general (and even when being very gentle), one can find that after a
while the upper cover is bent. This puts pressure on the recording
mechanism and can cause many problems. Under the cover of AIWA MD units
there are many screws. Pressing the buttons can loosen the screws and
oops! they fall directly on the laser unit. Last week I repaired a
AM-F75 having the ``DISC ERROR'' message on the display. The unit was
4 months old. I found a 2mm screw inside the laser unit, which moved
the lens from its position. The owner was lucky as it started working
fine after taking the screw out. As for pressure on other parts of
the MD. Putting too much pressure while holding the MD or a bent
cover can put extra force and pressure on moving parts inside the
MD. You will hear funny and sad noises as the motors are trying to
pass the obstacles.

Right disc: Some discs will cause us problems. Using types that have low
reflectivity will put extra stress on the laser unit. A too flexible housing on a disc can
bend the MD, some non-metal shutters on discs tend to bend, mainly in hot regions,
destroying the loading mechanism.

New designs of electronics for MD makes repairs expensive: The
DSP and control IC's in new Sony recorders e.g. MZ-R90/91 cannot be
removed from the board due to a packaging design in which the pins
are mounted under the chips and cannot be accessed
for de-soldering. When these chips malfunction they are impossible
to replace and the whole electronic board must be replaced at
considerable expense.

Tips - how to avoid some problems related to MD gear

Buy the right MD. If possible, buy a portable player. Those tend to have less
problems than recorders. Do your recordings on a MD deck, It's easier. If you
cannot have 2 MD's as stated above buy a recorder that is known to be strong as
possible. Try those having hard metal covers (MZ-R90/50) and those that are not
known to have recording problems. You may refer to opinions brought by
members of the MD Community Page.

Protect MD screws from falling. Apply transparent nail polish over the heads of the
screws to avoid their falling out.

Protect the recording mechanism. As much as possible avoid
dropping and vibrating the recorders. If you must run with a MD use a
player instead of a recorder. Place the disc inside the unit while it
is in parallel with the cover to avoid touching the sensitive
recording head. Many recording heads (mainly in AIWA MD's) get damaged
because of bad insertion of the disc. If you want to clean the optical
units do it with a cleaning disc, otherwise the cleaning must be done
with removed cover, so as to avoid damaging the recording head. Do not
use an air compressor to clean the inside of the MD. It may cause damage
to the recording head and other sensitive parts.

Use high quality cables for recording and playback. One
reason is that such a wonderful machine deserves good cables, but to be
more practical bad and cheap cables can deform the jacks and can
cause unexpected short circuits etc. I don't ask you to buy those
multi-$ cables, something in the middle will do the job. As all the
cables connected to the MD have 3.5mm (1/8'') plug, you may mistakenly
connect the wrong cable to a jack. To avoid this, mark the plugs with
a tape having the same color as the jack it is intended to be
connected to.

Use the correct PSU. For units having an original 110V
adapter, almost no problems are to be expected when used in the United
States and North America. In other countries use an original adapter
with the mains input rating the same as the mains of that country. For
e.g. UK it should be 240V, etc. You may use a step-down transformer
for 220 mains voltage countries if you have a 110V original PSU only
if the mains voltage in your country is known to be very stable. Pay
attention because some units come from Japan, where the mains voltage is
100V. For new models of SONY recorders working on 3V, even if the
mains voltage in your country is stable, a 220/110V transformer will cause
problems. You will have to use a 220/100V step-down transformer. 10%
difference in the input voltage (110/100) will cause 10% difference in
the output voltage and the MD's hate this situation.

How about countries with unstable mains voltage? (Some parts of
India and other countries). For those even an original Sony power
adapter with the right input voltage can cause damages. 60% of all new
Sony MD's we are repairing (MZ-R55/70/90/91) came to our desk due to
PSU problems. We solved this problem by developing a special line of
PSU's based on our knowledge of the electronics found inside the
MD. They are highly regulated and stabilized in output and self
adapted to any voltage between 100-250V. It means one can travel with
this MD all over the world, even to India and face no problem due to
electrical system differences. We have PSU's for 1.5V, 3V, 4.5V (for
Sony & Aiwa MD's), 5V (for all Sharp MD's), 6V (for MD's & Sony DAT),
9V, 10.5V (MZ-1), 12V etc. None of these PSUs we make has ever
damaged a MD and they live well for many years without complaint from
our clients.

Maintenance: Do not lubricate mechanical parts unless you are
well trained in fixing MD's. Only special lubricants will do the work
without making things worse. In extreme cases mechanical parts will
refuse to move due to dirt build-up around lubricated parts. Clean
the outer covers with a soft cloth. Check for dirt and clean all jacks
with a dry soft cloth. Avoid letting sand enter the machine. If you go
with the MD to the beach, hold it inside a well-protected bag. After
using the MD do not leave it connected to the mains unless you need to
charge the battery. A sharp spike over the mains will kill your MD and if
you have an MZ-R55 you may end up with the famous self-activating record
problem.

Replacement of an optical block assembly by a normal person: Yes or no.

To answer Eric's question:

``It might also be interesting to hear your assessment of how easily a normal person could
undertake something as serious as replacement of an optical block assembly.''

I will tell a small story. A few years ago
one of our clients brought us a mysterious machine called the MZ-2P.
He told us that the display shows DISC ERROR and asked us to repair
it. Among other things we do in electronics we repair all kinds of
electronic equipment. As for myself I admit I know to repair
airplanes as well as video cameras and complicated computers and
industrial equipment. I took the MZ-2P into my hands and opened its
covers, trying to start repairing it. It was the first time I held an
MD unit in my hands. After 2 minutes the MZ-2P stopped working
completely. No sign of life, no messages on the display, nada. It took
me 7 days to bring it back to the original DISC ERROR problem and
another long time to fix the problem. It was a very shocking
experience. Then I decided to take things seriously and I learned the
material very well, so today I am fixing 5 to 10 machines daily.

If one is about to fix his MD unit he should be very good in
electronics and mechanics. Second step - he must have the service
manual for the unit. Some new MD's cannot even be opened and still
remain undamaged unless you follow the steps outlined in the service
manual. In addition you must use high quality tools: precise
screwdrivers, excellent tweezers, anti static soldering iron, etc. You
must wear an antistatic wrist-strap in order not to damage the
components and especially the laser unit. It is a good practice to
wear rubber gloves so as to keep the internal parts as clean as
possible. If you don't have the service manual and still want to
continue, write down the location of each screw and use a small magnet
to hold the screws and other small metallic parts. Remove the bottom
cover and look inside. Are you impressed? I'm always very
impressed. Now I would suggest that you close it back up and do not
attempt to fix it by yourself. If you are well experienced with
repairing MD's you probably don't need my advice on how to repair them
and if you are not, my best advice to you is to close it and do not
attempt to make things worse.

Addendum:

I asked David for clarification about the number of machines he was
repairing, 10 a day sounded like an extraordinary quantity in a small
country where MD is expensive and not so popular. He responded as follows.

Let me explain to you the situation with MD in Israel. During
the last 3 years it has become very popular especially among teenagers.

The problem is the high prices of MDs in my country. This situation
is due to almost 100% customs and 17% vat. Add the profit of the
importer/distributor/retailer and you get an MZ-R55 for $500, MZ-R91
for $600 etc. Ispar Ltd, the representative of Sony in Israel, is the
only representative that sells Sony MDs. The Aiwa and Sharp importers
do not import MD gear at all, neither do they service those
machines. Of course there are shops not related to the importers that
import MDs from dealers in Japan and other countries. I would say
that most MDs in Israel are bought outside of Israel, mainly
in the US and Far East by people visiting those countries, or at a
tax-free shop at our international Airport when one travels. You may
buy at those shops without paying customs for MDs priced no more than
$200. These days they sell Sharp model MD-MT15.

Regarding repairs the situation is more complicated. Sony in Israel
recognizes guarantees for MDs bought in their shops in Israel only. So
even if you have an international guarantee from Sony they will still
charge you fully. Also there is a laboratory for MDs bought at the
free tax shop in the airport. All the others have to look for service
and pay for it. At Sony you pay very much for every repair. Not
everybody is ready to pay those high prices, and on the other hand I
believe my shop is almost the only one that is ready and capable of
repairing all MDs. It is not easy, as it is difficult for me to get
all the parts I need, but as we give this matter our greatest
attention we manage to repair almost all the MDs brought to
us. Yesterday, for the first time, I repaired a JVC MD unit. It is a
very nice machine and looks like Palm Pilot, but is rather heavy. It
came to me completely dead due to wrong PSU. In addition there was no
sound coming from the earphone socket, and it was not recording. I do
not have any documentation or service manual for this MD unit but I
fixed it completely. A transistor in the power circuit was damaged. At
the amp output 2 "muting" transistors where exploded completely and I
had to guess what the original ones were. The recording head was bent
completely but somehow not broken so I could fix it, and now I have
another happy client.

As for the numbers. I respect your question and your effort to have
real facts in the texts placed at the site you are managing. To be
more specific, I hold daily more than 10 MD units. Some of them have
very small problems, which I repair at the counter (missing screws,
etc). Full repairs I do on 70 - 100 MDs monthly. Regarding
pictures. In the future I will try to send you more interesting
pictures than simply a picture of myself, i.e. pictures of the tools
I'm working with, special tools I've made myself, the measuring
equipment etc.